[en] We present a catalog containing the measurements of 2262 sources, including 334 extended sources, 1915 point sources, and 13 known QSOs, in five SDSS passbands. Of these objects, over 1600 are measured in 15 fields covering 0.5 deg2, with a limiting magnitude of r^*<19.5, similar to the photometric limit of the SDSS spectroscopic survey. Color plots of the data show that stars, galaxies, and quasars are fairly well separated by color alone. The stellar locus populates a ribbon-like subset of color-color-color space. It is shown that stars, galaxies, and QSOs tend toward the same fundamental plane in three-dimensional color space. The stars are compared with synthetic photometry from Kurucz models; the agreement is consistent with the errors in the data. The stellar locus moves in color space by about a tenth of a magnitude from r^*=14 to r^*=19.5. The shift is consistent with a shift in the metallicity from about [Me/H] = -1 to [Me/H] = -2. We compare this with previously measured metallicity gradients as a function of distance from the galactic plane. (c) (c) 1999. The American Astronomical Society

[en] We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

[en] We develop a new approach for studying flux anomalies in quadruply imaged fold lens systems. We show that in the absence of substructure, microlensing, or differential absorption, the expected flux ratios of a fold pair can be tightly constrained using only geometric arguments. We apply this technique to 11 known quadruple lens systems in the radio and infrared and compare our estimates to the Monte Carlo based results of Keeton et al. We show that a robust estimate for a flux ratio from a smoothly varying potential can be found, and at long wavelengths those lenses deviating from this ratio almost certainly contain significant substructure.

[en] We have used the Very Large Array (VLA) FIRST survey and the Automated Plate Measuring Facility (APM) catalog of the Palomar Observatory Sky Survey I (POSS-I) plates as the basis for constructing a new radio-selected sample of optically bright quasars. This is the first radio-selected sample that is competitive in size with current optically selected quasar surveys. Using only two basic criteria, radio-optical positional coincidence and optical morphology, quasars and BL Lac objects can be identified with 60% selection efficiency; the efficiency increases to 70% for objects fainter than 17 mag. We show that a more sophisticated selection scheme can predict with better than 85% reliability which candidates will turn out to be quasars. This paper presents the second installment of the FIRST Bright Quasar Survey (FBQS), with a catalog of 636 quasars distributed over 2682 deg2. The quasar sample is characterized and all spectra are displayed. The FBQS detects both radio-loud and radio-quiet quasars out to redshift z>3. We find a large population of objects of intermediate radio loudness; there is no evidence in our sample for a bimodal distribution of radio characteristics. The sample includes ∼29 broad absorption line quasars, both high and low ionization, and a number of new objects with remarkable optical spectra. (c) (c) 2000. The American Astronomical Society

[en] The wavelength dependence of atmospheric refraction causes differential chromatic refraction (DCR), whereby objects imaged at different optical/ultraviolet wavelengths are observed at slightly different positions in the plane of the detector. Strong spectral features induce changes in the effective wavelengths of broad-band filters that are capable of producing significant positional offsets with respect to standard DCR corrections. We examine such offsets for broad-emission-line (type 1) quasars from the Sloan Digital Sky Survey (SDSS) spanning 0 < z < 5 and an airmass range of 1.0-1.8. These offsets are in good agreement with those predicted by convolving a composite quasar spectrum with the SDSS bandpasses as a function of redshift and airmass. This astrometric information can be used to break degeneracies in photometric redshifts of quasars (or other emission-line sources) and, for extreme cases, may be suitable for determining 'astrometric redshifts'.On the SDSS's southern equatorial stripe, where it is possible to average many multi-epoch measurements, more than 60% of the quasars have emission-line-induced astrometric offsets larger than the SDSS's relative astrometric errors of 25-35 mas. Folding these astrometric offsets into photometric redshift estimates yields an improvement of 9% within Δz ± 0.1. Future multi-epoch synoptic surveys such as LSST and Pan-STARRS could benefit from intentionally making ∼10 observations at relatively high airmass (AM ∼ 1.4) in order to improve their photometric redshifts for quasars.

[en] We use multiepoch quasar spectroscopy to determine how accurately single-epoch spectroscopy can locate quasars in emission-line parameter space in order to inform investigations where time-resolved spectroscopy is not available. We explore the improvements in emission-line characterization that result from using nonparametric information from many lines as opposed to a small number of parameters for a single line, utilizing reconstructions based on an independent component analysis applied to the data from the Sloan Digital Sky Survey Reverberation Mapping project. We find that most of the quasars are well described by just two components, while more components signal a quasar likely to yield a successful reverberation mapping analysis. In single-epoch spectroscopy the apparent variability of equivalent width is exaggerated because it is dependent on the continuum. Multiepoch spectroscopy reveals that single-epoch results do not significantly change where quasars are located in C iv parameter space and do not have a significant impact on investigations of the global Baldwin effect. Quasars with emission-line properties indicative of higher L/L _Edd are less variable, consistent with models with enhanced accretion disk density. Narrow absorption features at the systemic redshift may be indicative of orientation (including radio-quiet quasars) and may appear in as much as 20% of the quasar sample. Future work applying these techniques to lower-luminosity quasars will be important for understanding the nature of accretion disk winds.

[en] We present the discovery of only the second radio-selected z ∼ 6 quasar. We identified SDSS J222843.54+011032.2 (z = 5.95) by matching the optical detections of the deep Sloan Digital Sky Survey Stripe 82 with their radio counterparts in the Stripe 82 Very Large Array Survey. We also matched the Canadian-France-Hawaiian Telescope Legacy Survey Wide with the Faint Images of the Radio Sky at Twenty cm survey but have yet to find any z ∼ 6 quasars in this survey area. The discovered quasar is optically faint, z = 22.3 and M₁₄₅₀ ∼ -24.5, but radio bright, with a flux density of f_1.4GHz,peak = 0.31 mJy and a radio loudness of R ∼ 1100 (where R ≡ f_5GHz/f₂₅₀₀). The i - z color of the discovered quasar places it outside the color selection criteria for existing optical surveys. We conclude by discussing the need for deeper wide-area radio surveys in the context of high-redshift quasars.

[en] Extended extragalactic radio sources have traditionally been classified into Fanaroff and Riley (FR) I and II types, based on the ratio r_s of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source (r_s ≡ S/T). In this paper, we examine the distribution of various physical properties as a function of r_s of 1040 luminous (L ∼> L_*) extended radio galaxies (RGs) at z < 0.3 selected with well-defined criteria from the SDSS, NVSS, and FIRST surveys. About 2/3 of the RGs are lobe dominated (LD) and 1/3 have prominent jets. If we follow the original definition of the FR types, i.e., a division based solely on r_s , FR I and FR II RGs overlap in their host galaxy properties. However, the rare LD sources with r_s ∼> 0.8 and [O III] λ5007 line luminosity >10⁶ L_sun are markedly different on average from the rest of the RGs, in the sense that they are hosted in lower mass galaxies, live in relatively sparse environments, and likely have higher accretion rates onto the central supermassive black hole (SMBH). Thus, these high emission line luminosity, high-r_s LD RGs, and the rest of RGs form a well-defined dichotomy. Motivated by the stark differences in the nuclear emission line properties of the RG subsamples, we suggest that the accretion rate onto the SMBH may play the primary role in creating the different morphologies. At relatively high accretion rates, the accretion system may produce powerful jets that create the 'classical double' morphology (roughly corresponding to the LD sources with r_s ∼> 0.8 and emission lines); at lower accretion rates, the jets from a radiatively inefficient accretion flow generate radio lobes without apparent 'hot spots' at the edge (corresponding to the majority of LD sources). At slightly lower accretion rates and in galaxies with dense galactic structure, sources with prominent jets result. It is possible that while the high accretion rate systems could affect sub-Mpc scale environments, the jets from lower accretion rate systems may efficiently suppress activity within the host galaxies.

[en] Clustering measurements of obscured and unobscured quasars show that obscured quasars reside in more massive dark matter halos than their unobscured counterparts. These results are inconsistent with simple unified (torus) scenarios but might be explained by models in which the distribution of obscuring material depends on Eddington ratio or galaxy stellar mass. We test these possibilities by constructing simple physical models to compare to observed active galactic nucleus populations. We find that previously observed relationships between obscuration and Eddington ratio or stellar mass are not sufficient to reproduce the observed quasar clustering results ($⟨<!--\; ???\; -->\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}}/M_{\odot <!--\; ???\; -->}⟩<!--\; ???\; -->={12.94}_{-<!--\; ???\; -->0.11}^{+0.10}$ and $⟨<!--\; ???\; -->\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}}/M_{\odot <!--\; ???\; -->}⟩<!--\; ???\; -->={12.49}_{-<!--\; ???\; -->0.08}^{+0.08}$ for obscured and unobscured populations, respectively) while maintaining the observed fraction of obscured quasars (30%–65%). This work suggests that evolutionary models, in which obscuration evolves on the typical timescale for black hole growth, are necessary to understand the observed clustering of mid-IR-selected quasars.

[en] Broad absorption-line (BAL) features in quasar spectra reveal an unambiguous signature of energetic outflows from central supermassive black holes, and thus, BAL quasars are prime targets for investigating the potential process of luminous quasar feedback on galaxies. We analyzed the rest-UV spectrum of an “overlapping trough” iron low-ionization broad absorption-line quasar (FeLoBAL) SDSS J135246.37+423923.5 using the novel spectral synthesis code SimBAL and discovered an extraordinarily fast and energetic BAL outflow. Our analysis revealed outflow velocities reaching $\sim <!--\; ???\; -->-<!--\; ???\; -->38,000\mathrm{k}\mathrm{m}{\mathrm{s}}^{-<!--\; ???\; -->1}$ with a velocity width of $\sim <!--\; ???\; -->10,000\mathrm{k}\mathrm{m}{\mathrm{s}}^{-<!--\; ???\; -->1}$, which is the largest FeLoBAL outflow velocity measured to date. The column density of the outflow gas is log$N_{\mathrm{H}}\sim <!--\; ???\; -->23.2({\mathrm{c}\mathrm{m}}^{-<!--\; ???\; -->1})$ with the log kinetic luminosity $\mathrm{l}\mathrm{o}\mathrm{g}{L}_{\mathrm{K}\mathrm{E}}\sim <!--\; ???\; -->48.1$ (erg s⁻¹), which exceeds the bolometric luminosity of the quasar and is energetic enough to effectively drive quasar feedback. The energy estimate for the outflow is far greater than the estimates from any BAL object previously reported. The object also shows “anomalous reddening” and a significant scattered component that we were able to model with SimBAL. We found the first definitive case for radiation filtering in an additional zero-velocity absorption component that required an absorbed continuum to produce the particular absorption lines observed (Mg ii, Al iii, and Al ii) without also producing the high-ionization lines such as C iv.